Internal combustion engine



June 15,` 1943. A. c. sAMPlETRo INTERNAL COMBUSTION ENGINE .I

8 Sheets-Sheet 1 Filed June l, 1940 .RNE

June 1943. Akc. sAMPlETRo 2,321,943

INTERNAL coMUsTIoNBNc-INE 8 Sheets-Sheet 2 Filed June 1, 1940 June; 15, 1943. A. c. sAMPn-:TRO y2,321,943

INTERNAL COMBUSTION ENGINE l Filed June 1, 1940 8 sheets-sheet rs June 15, 1943. v A. c. sAMPxETRov 2,321,943 v INTERNAL coMBUsTIoN ENG'INE Filed une 1`, 1940 sheets-sheet 4 lNvE N'ro&

June l5, 1943. A. c. sAMPlETRo INTERNAL COMBUSTION ENGINE Filed June 1, V1940 8 Sheets-Sheet 5 June 15, 1943. A. c. sAMPn-:TRO 2,321,943

INTERNAL COMBUSTION ENGINE Filed June 1, 1940 a sheets-sheet e la Ach l@ Charles Sompe' ro 1N vr; N To rc L* v ATTy,

June 15, 1943.

A. C. SAMPIETRO INTERNAL coMBUsTIoN ENGINE Filed June 1, 1940 8 Sheets-Sheet, 7

INVENTOR lchille Chorlg Sdmpietro im AT'oRNEY.

June 15, 1943. j A. c. SAMPIETRO 2,321,943

' INTERNAL COMBUSTION ENGINE K Filed June 1, 1940 l I s sheets-sheet a \NVENTOQ,

` the engine is running,

l Patented' June v15,

UNITED STATES PATENT ori-*ics Maasai. orlon ENGINE Achille Charles Sampietro. Coventry, England Application June 1, 1940, Serial No. 338,292

In Great Britain June 7. 193s s claims.' (ci. 12s-5s) This invention relates tol internal-combustion engines of the kind having two crank-shafts and is especially but not exclusively concerned with such engines which are intended for use on aircraft.'

An object of this invention is to provide such an engine having improved means for transmitting the power from the two crank-,shafts to' a common output shaft, such for instance as an air-screw shaft, whereby vibrations arising in either crank-shaft are prevented or largely prevented vfrom anecting the other crank-shaft or the output shaft.

A furtherA object is including one or more pairs of cylinders. each having a common combustion chamber, in which the compression ratio can be varied by. altering the phase relationship of the crank-shafts while detonation when the charging pressure is temporarily increased for the purpose of boosting the power output above the continuous full-load rating.

Another object is to provide, in such an enginehaving one or more pairs of cylinders, each havfor example to prevent,

i assembly, taken on the Ito provide such an engine ing a common combustion chamber, resilient coupling and damping means serving both to reduce or prevent the transmission of vibrations arising in the crank-shafts and to vary automatically the phase relationship o! thel crank-shafts and thereby the compression ratio with variation in load.

Yet another object is gine having one or more pairs of cylinders,

to provide in such an eneach having a common combustion chamber, a servooperated phase-adjusting coupling means in the gearing that constrains the crank-shafts to rotate at equal speeds.

A further object is to provide an engine operating on the two-stroke cycle and provided with spark ignition means, which is capable of having its power output temporarily boosted.

Further objects and advantages ofthis invention will be apparent from the following descrip- .tion of embodiments thereof illustratively exemplied vin the accompanying drawings, in which- Fig. 1 is a diagrammatic side elevation of an aero engine,

Fig. 2 is a diagrammatic plan of the same engine. Fig. 3 is a. diagrammatic front end elevation of the same engine,

Fig. 4 is a cross section to' a larger scale through a rpair'of cylinders, taken for example on the line 4-14 in Fig. 1,

" site directions.

are displaced in the following order directions of displacement Fig. 5 is a section of a partof the engine to a still larger scale, taken on the line 5-5 in Fig. 4,

Fig. 6 is an underside elevation of a part of the engine, developed on the line tin Fig. 4,

Fig. 'I is a sectional plan of the turbo-blower line 1-l-1 in Fig.' l, Fig. 8 is a section -to a larger scale of a part of Fig. 7,

Fig. 9 is a sectional and reduction gearing,

Fig. 10 is a section on Fig. 11 is a section of a modified part of the gearing.

Fig.- 12 is an electrical circuit diagram of control mechanism for the part shown inA Fig. 11, and

Fig. 13 1s a diagram of parts associated with the turbine.

I'heexample shown in Figs.. 1-10 is atwo-stroke aero engine having two crank-shafts and twelve pairs of working cylinders, the each pair-having a common combustion chamber. Referring to Figs. 1 to 6 a crank-case 20 is' split on ythe longitudinal vertical middle plane oi' the engine and in it are journalled two six-throw crank-shafts 2| and 22.I These crank-shafts are coupledl bygearing in a gear-case 23 which constrains them to rotate at equal speeds in oppo- The crankpins of each shaft' at angles of Nos. l, 4, 2, 6, 3, 5, the being opposite in the two shafts. To each side of the crank-case 2l are secured six light alloy cylinder blocks 2 4 each containing two cylinder bores 25 and 26 defined by hardened liners. The axes-of these bores are inclined to each other at 415 deg. in such a inanner that their head ends are closer together than the ends nearer the crank-shafts. Each cylinder block has a light alloy head 21, which is recessed to form a combustion chamber' 28 common to the side elevation of coupling deg.vfrom each other:

two cylinders of the block.' A fuel-'injection nozzle 23 and two sparking plugs 30 are tted in each head 21 and open into the combustion charn- The pistons 35 onthe starboard side of the two cylinders oi' engine are connected to the respective crankpins of the shaft 22 by master connecting rods- 3l, while the pistons 35' on the port side are connected to the respective rods il by slave connecting rods Si). The normal phase relationship of the two crank-shafts may be such that the crankpins of the shaft 2i that controls the exhaust timing lead by 39 deg. the corresponding crank pins of the shaft 22 that controls the scavenge timing as shown in Fig. d, where the directions of rotation are indicated by arrows. The depths of all the ports 32 and 3d and their positions relative to the ends of the respective cylinder bores may be uniform and such that the duration of opening of any port represents 145 deg. of crank rotation.

The engine is scavenged and charged with air by a centrifugal blower ill directly coupled to an exhaust-gas-driven impulse turbine di (Figs. l and 2). As shown in Fig.. 7 the blower has two impellers i2 and ed arranged back to back and of unitary construction. These impellers draw air from intake ports dit and d in the blower casing and discharge into volute chambers 416 and dl leading respectively to port and starboard de- I livery elbows 48 and 99. These connect respectively with air manifolds |00 and l0! provided with branches |02 communicating with the scavenging ports 36. l l

A tubular shaft 59 is-bolted to the hub 5| of the impellers 92 and d3 and to the hub of a turbine rotor 52 having a single row of limpulse blading 53. Two ball bearings 54S capable of taking journal and thrust loads have their inner races fast on. a spigot-55 on the rotor 52 and their outer races fast in a bearing housing 56 forming a part of the turbine frame 5l and sealed with respect to the rotor 52 by a labyrinth oil-seal 58. Dierential expansion of the fixed and rotary parts is accommodated by the bearing means at the blower end which are` shown in detail in Fig. 8. Two ball bearings 59 have their inner races fast on a sleeve 60 fixed to the hub 5| while their outerV races are mounted in a ring 6| which has a close sliding fit in a sleeve 62 xed in a boss 63 of the blower casing. A labyrinth oil-seal 64 is formed between one end of this sleeve and a ring 65 clamped with 'the inner bearing races on'the rotary sleeve 60 by nuts 66. The other end of the sleeve 6| is provided with an inturned flange 51 against which abut compression springs 68 held in a ring 69 reacting against the inner end of the fixed sleeve 62. Differential expansion is accommodated by sliding ofthe ring 6| in the sleeve 62, the springs 60 ensuring a constant axial clearance in the labyrinth oil-seal 64.

The turbine is provided with a nozzle-box |03 into which debouch twelve exhaust pipes |04 leading respectively from the individual exhaust ports 32. These pipes are so arranged that the differences between their lengths are slight.

, O'ne form of the gearing contained within the gear case23 is shown in Figs. 9 and 1 0; the various ball and, roller bearings are included, butV their housings and the case are omitted. A gearwheel '|0 is rigid with a reduction gear pinion these two elements being journalled in bearings 12, 13 and T4 coaxially with the crank-shaft 22. An air-screw shaft 15 is journalled in bearings 16, |l and 18 co-axial with the crank-shaft 2| and is splined to a reduction gear-wheel 19 mesh..

1 ing with the pinion 1|. A gear wheel 80 is journalled on lbearings 82 and 82' co-axially with the crank-shaft 2| andmeshes with the gear wheel lil. The gear wheels 'i9 and biliare coupled respectively to the crank-shafts 22, and 2| lby damped resilient couplings serving to reduce the transmission of torsional vibration from the crank-shafts to the gearing, As these couplings are similar in design, only that between the crank-shaft 22 and the gear wheel 'lll will be described in detail. A hub 8i is splined to the crank-shaft 22 and provided with radial vanes |99 and a flange 83. The interior of the gearwheel lll is hollow and provided with vanes 34 alternating with the vanes |08. The flange 83 is sealed with respect to the wheel lil by a ring d5 of synthetic oil-resisting rubber having projections 85 between the vanes |08 and the rim of the wheel lil. Pads 8l of similar rubber are disposed between the vanes 84- and the hub 8i and are provided' with iiaps 88 which co-operate with oil inlet ducts 89 to form non-return valves. The ducts 99 are supplied with oil from a cenirifugal collecting channel 90. Rebound compression springs 9| are disposed between the trailing faces of the vanes |08 and the leading faces of thev next following vanes 9B, and drive compression springs 92, which are stiffer than the springs 9|, are disposed between the trailing faces of the vanes S4 and the leading faces of the next following vanes |08. In operation, the chambers between the vanes become filled with oil entering through the duct 89, the springs providing the resilient driving connection and the resistance imposed by the rubber parts 86 and 0l tothe l'escape of oil providing the `necessary damping. The resilient coupling in the wheel 80, in this example, has a lower torsional stiffness thanvthe coupling in the wheel 10- for a purpose which will be hereinafter discussed.

The gearing also includes an auxiliary drive wheel 96 mounted rigidly with the wheel 89 and meshing with a pinion 91 integral with' a timing shaft 99 which drives dual ignition contactbreaker and distributor units 93 (Figs. 1 and 3) and a battery of fuel-injection pumps 95. Twelve of these pumps feed the injection nozzles 29 respectively by pipes 94, which are shown broken away.` Two additional `pumps. are provided, de` livering to pipes 99; for a purpose which will be mentioned hereinafter. The quantity of fuel delivered at each stroke by the twelve pumps feeding the pipes 94 is controllable in the conventional 'manner by a control lever |05, and the fuel delivery of the two additional pumps feeding the pipes 99 is independently controllable by a lever |06. The pipes 99 lead respectively to two ring pipes |06 (Fig. 13) encircling the turbine casing 51 and connected by branches |01 to fuel injection nozzles |09 inserted in the exhaust pipes |04 near the points where they debouch into the nozzle box |03. Each ring pipe supplies nozzles on alternate exhaust pipes.

This engine operates as follows. Exhaust gases passing through the pipes |04 to the tur# bine 4| maintain the turbine rotor in rotation and the turbine drives the blower impel1ers42 and l43 which draw air vfrom the atmosphere through the inlets 44 and 45 and deliver it under increased pressure to the air manifolds |00 and 10|.' It will be assumed that the charge in apair ofcylinders has just been ignited by the spark- `ing plugs 30 and that -the pistons are moving on their out-stroke from the position shown in'- Fig. 4. 'I'he piston 3| being in advance of the pass through the appropriate pipe |04 to the turbine. When the pressure in the cylinders has fallen suillciently, the piston 35 uncovers the scavenging port 36, and compressed air from'the manifold or |0| sweeps through'the cylinject a charge of a relatively volatile fuel through the nozzle 26 into the turbulent mass of air compressed in the combustion chamber where it is ignited by the sparking plugs 30. A

The power out/put of the engine is regulated by varying the`delivery of -thefuel pumps lto the homies 28 by means of the control lever |05. When the engine is running under light load, the 'phase displacement between the crank-shafts is the minimum, the compression ratiol is the maximum and consequently the fuel consumed per horse-power-hour is the minimum; As the fuel supply is increased and the engine torque consequently rises, the-resilient coupling associated with the crank-shaft 2| thatl controls the exhaust ports yields more than the stiffer resilient coupling associated with the crank-shaft 22 that controls ,thel scavenge ports, so that the phase displacement between the two crank-shafts' increases. Consequently the compression ratio decreases, as is required to prevent detonation, and the exhaust port opens and closes earlier in the working cycle oi' each pair of cylinders. As the expansion ratio in the working cylinders is reduced, the exhaust gases will contain more re' sidual energy per unit weight and the turbine will therefore run faster so that the blower operates to increase the amount of supercharge.

The two -additional fuel pumps feeding the injection nozzles |09 in the exhaust pipes serve temporarily to increase the power output of the engine to substantially more than its normal maximum continuous rated output, for example for the purpose of taking of! a heavily loaded aircraft. Since at all times part of the gases leaving the exhaust ports of the working cylinders consists of excess air, this air serves to burn the fuel injected through the nozzles |08 when the control lever |06 is actuated. In this way the available heat drop in the exhaust gases is increased. and consequently the power available for driving the blower so that the charging pressure of the engine and its net power output are increased.

The engine hereinbefore described may be modified by substituting positive means, in place of the'resilient` means, for varying the phase relationship of the two crankshaft/s. One form of such positive means is shown in Fig. 11 associated with the connecting gear wheel A and the crank-shaft 22A, which correspond to the parts 10 and 22 hereinbefore described. The resilient damped coupling between the other crankv shaft'2 and the gear wheel 80 that meshes with the wheel 10A is relativelyrstlif. The kwheelA 10A can be advanced and retarded relatively to the shaft 22A by the servo-mechanism now to be described. A hub having internal helical splines |2| is slidably engaged with co-operating splines y3 vided with straight external splines |24 slidablyengaging with vinternal splines |25 in thebore of the wheel 10A. The hub |20 and the rim |23 are provided with interlaced cylindrical flanges |26 and |21 and-rubber rings are disposed in the annular spaces so formed and bonded to the hub and rim portions, forming a relatively stiff resilient coupling. A ball thrust bearing |20 has its inner race clamped to the hub |20'by a bracket ring secured to this hub by screws |3I. The outer race of the bearing |28 is rigid with a ring |32 havingan external screw thread |33 cooperating with an internal screw thread |34 in the shaft of the pinion 1|A. A crown wheel |35 fixed by screws |36 to the ring |32 meshes with bevel pinions |31 integral withl shafts |38 journalled in -brackets |38 on the ring |30. Bevel wheels |40 fixed to the shafts |38 mesh with a bevel pinion |4 journalled by bearings |46 and |41 in brackets |42 on the ring |30. The pinion |4| is integral with a tubular externally splined shaft |43 on which is slidably engaged an internally splined element |44 of a The bearings of the universal. coupling |45.

washer |48 and a pinion |4| are retained by a bar |48 clamped together by a hollow bolt |58 the bar |48 passing through a transverse slot |5| in the shaft |43. The joint is coupled by a tubular shaft |52 and a second universal joint |53 to the hollow shaft |54 of a reversible serieswound electric motor |55 which is fixed within: the shaft of the pinion v1|A for rotation there'J with. -Within the motor casing are provided a l`reversing contactor and a limit switch, the externalfelectrical connections being made through slip rings |56, |51 and |58. The limit switch is actuated by a rod |58-slidably mounted in the hollow motor shaft and in the bore Aof the bolt |56 and provided with-abutm'entsl |60 and |6| co-operating with the ends of this bolt. TheA Y electrical control mechanism is shown diagram--I matically in Fig. 12.

|22on the shaft 22A. A rim |23 is Dro- 75 A battery |62 has one terminal earthed and the other terminal connected to a brush |63 izo-'operating with the slip ring |56 which in turn is connected to a contact blade |64 of a normally-open contactor. The contact blade |64 can connect alternatively with conductors |65 and |66 which respectively include the two contact breakers of the limit switch |68 and connect with the terminals of the motor field coil` |61. The armature |68 of the motor is connected at one side to earth and at the other side by a conductor |10 toa second contact blade |1| `oi the contactor. The blade |1| can connect alternatively with conductors |12 and |13 leading to the terminals of the eid coil |61.- .A controll switch blade |14 is connected to the live terminal of the battery andcan contact alternatively with conductors leading to brushes |15 and Nico-operating respectively with theslip rings |51 and |58 which are connected to earth through the energising coils |11 and |18l of the contactor. This mechanism operates as follows. The parts will be assumed to be in the configuration shown `in Figs.`11 and I2, that is to say the relative angular position of the wheel 10A vand the shaftA itl and lll to earth and rocks the contacter armature clockwise, so that the blade 66 contacts with the conductor 55 and the blade ili with the conductor i713. Current now flows through the following circuit: it, E56, itt, it@ (closed contacts), it, 961, 873, ili, il@ and it@ to earth. The motor thus beginsto rotate and through the reduction gearing rotates the ring |32 relatively to the shaft of the pinion 'HA in such a direction that this ring is constrained by its screw-thread to move to the left (as seen in Fig. 1l). Since the assembly of hub i2@ and rim 23 is coupled to the ring l32 by the thrust bearing H29, this assembly is also slid to the left, the helical splines l2l and mi co-operating to vary the angular relationship of the wheel WA and the shaft 22A and thus increase the phase advance of the crank-shaft 2l relatively to the crank-shaft 22A. The rod H59 is also free to move 'to the leftlso that the limit switch can assume its mid position in which both contact breakers are closed. If the control blade H4 is now returned to its mid position, the motor- |55` stops. If however the control blade is kept to the right, as the parts approach the other'limit of their range of adjustment, the head of the bolt use strikes theV abutment ist on the rod 59 and opens the limit switch contact breaker in the conductor S65 so that the motor stops. Adjustment in the reverse direction is effected by moving the control blade |14 to the left so that current. ows through the elements H6, E58 and |18 to earth and rocks the contactor armature counterclockwise, so that the blades E64 and I'II contact respectively with the conductors E66 and |12. Current now iiows through the following circuit: |63, l'56, |64, 68, IE6, H51, i12, I'II, |10 and |69 to earth, the direction of dow through the eld coil l6l being opposite .to that occuring when the control blade lll was moved to the right. The motor accordingly runs in the reverse direction, causing the slidable elements of the adjusting gear to move back to the right. The adjusting vmovement can be stopped at any de,- sired point, vand resumed in either direction.

The control blade |16 is capable of automatic actuationin response to lvariation in charging pressure, forinstance. on operation of the boosting fuel nozzles-provided in the exhaust pipes leading to the turbine. Such an automatic control is shown in Fig. 12. The control blade |14 is connected by a rod H to the movable wall of a spring-loaded anaeroid capsule l li having theother wall fixed. The capsule is contained in an air-tight chamber II2 communicating through a damping restriction H3 with a duct Ill leading to one of the air manifolds, say |00. The duct may be provided with an isolating valve H5. When the valve I I is open and the manifold pressure exceeds a predetermined value, the capsule III is contracted and moves the blade H4 to the right to energise the slip ring |51, so that the exhaust-controlling crank-shaft 2| is given the maximum lead in relation to the scavenge-controlling crank-shaft 22A and the compression ratio is correspondingly reduced. When the manifold pressure thereafter lfalls to a predetermined value, the capsule lll expands and moves the control blade H4 to the left so that the slip ring 58 is difference between the to its minimum value.

I claim: 1. An internal-combustion engine including a plurality of -pairs of cylinders, the two cylinders energised and the phase crank-shafts is reduced of each pair having a common combustion cham-- ber, pistons in said cylinders, two crank-shafts operatively connected respectively to the two pistonsof each pair of cylinders, a supercharger forl charging said cylinders, gearing constraining said crank-shafts to rotate at equal speeds, and

means for temporarily boosting the power output of said engine and including a control member operation of which serves to increase the delivery pressure of said supercharger and means associated with said gearing for varying while the engine is running the angular relationship of said crank-shafts and thereby reducing the conipression ratio of said pairs of cylinders when said delivery pressure is increased.

2'. An internal-combustion engine including a plurality of pairs of cylinders, the two cylinders of each pair having a common combustion chamber, pistons in said cylinders, two crank-shafts operatively connected respectively to the two pistons of each' pair of cylinders, a supercharger for charging said cylinders, means for controlling the deliverypressure of said supercharger, a power-output shaft drivably connected to said crank-shafts'by gearing which constrains said crank-shafts to rotate at equal speeds and which includes a resilient connection capable of yielding under torque in one of said crank-shafts and thereby varying the phase relationship of said crank-shafts automatically in response to variations in power output.

3. An internal-combustion engine including a pair of cylinders having a common combustion chamber, pistons in said cylinders, two crankshafts operatively connected with said pistons respectively, and` gearing constraining said crank-,shafts to rotate at equal speeds, said gearing including two power-transmitting elements normally rotatable as one and constrained to move helically with respect to -each other when relatively displaced in the axial direction, a servornotor having a body constrained to rotate with one of said elements and an output member operatively connected to theother of said elements for relatively displacing said elements axially, and a reversing controller for said servo-motor.

4. A two-stroke internal-combustion engine including a plurality of pairs of cylinders, pistons in said cylinders, the-two cylinders of each pair having a common combustion chamber and respectively piston-controlled exhaust and scavenging ports, two crank-shafts operatively associated respectively with the pistons controlling said exhaust ports and the pistons controlling said scavenging ports, a supercharger. a duct communicating continuously between said supercharger and said scavenging ports, control means operable for temporarily boosting the delivery of said supercharger, gearing constraining said crank-shafts to rotate at equal speeds and including means operating in response to increase in delivery of said supercharger for increasing while the engine is running the phase difference ofy the pistons associated respectively with said crank-shafts, andthereby reducing the compression ratio and advancing the exhaust timing of said pairs of cylinders;

5. A two-stroke internal-combustion engine including a plurality of pairs of cylinders, each pair having a common combustion chamber, and one cylinder of each pair having an exhaust port while the other has a scavenging port, pistons in said cylinders controlling said ports, two crankshafts actuating respectivelysaid exhaust-controlling pistons and said scavenging-controlling compression strokes, spark vignition Ameans for igniting the fuel so injected and means associated with said gearing and capable of increasing the phase displacement of said pistons and thereby reducing the compression ratio of said pairs of cylinders in response to increase in the supercharging pressure.

6. An internal-combustion engine comprising two rows of cylinders, two multi-throw crankshafts disposed parallel to each other, pistons in one of said rows of cylinders operatively connected to one of saidcrank-shafts, pistons inthe other of said rows of cylinders operatively connected to the other of said crank-shafts, an output shaft,A coupling and reduction gearing bef tween said three shafts for constraining said crank-shafts to rotate at equal speeds and said output shaft to rotate at a lower speed, said gearing including two gear wheels connected respectively to said crank-shafts by damped resilient couplings.

7. An internal-combustion engine as claimed in claim 6 and comprising auxiliaries required to be actuated in timed relation to said crankshafts, wherein a timing shaft for driving said Aauxiliaries is drivably connected to said vgearing at a point therein on the output-shaft side of said damped resilient couplings.

`8. An internal-'combustion engine including a pair of cylinders having a common combustion having two relatively'movable parts one of which is fixed to one of said two elements and the other of which is operatively connected to said third element for axially moving the same, and a reversin'g` controller for said servo-motor.

9. An internal-combustion engine including a pair of cylinders having a common combustion chamber, pistons in said cylinders, two crank shafts operatively connected with said pistons respectively, gearing constraining said crankshafts to' rotate at equal speeds, said gearing including a, hollow third shaft co-axial with the rst of said crank-shafts, a gear wheel on said third shaft meshing. with a gear wheel con- :trained to rotate with the second of said crankshafts, a coupling member slidably splined to said first crank-shaft and vto said third shaft by splined connections at least one of which is helically disposed, a servo-motor having abody xed within said third shaft and an output shaft ro' tatable relatively to said body, a screw-threaded ring co-operating with a screw thread in said third shaft, a thrust bearing connecting said ring to said coupling member, auxiliary gearingdrivably connecting the output shaft of said servomotor to said ring for rotating the latter relatively to said third shaft, and a, reversing'controller for said servo-motor.

ACHILLE CHARLES SAMPIETRO. 

